1. Field of the Invention
The present invention relates generally to a rotary type compressor for an air-conditioning unit or the like and more specifically to a rotary compressor which includes a passage structure which enables the temperature of the bearings which rotatably support the drive shaft of the compressor to be maintained at a desirable level and prevent undesirable dilution of the lubricant therein.
2. Description of the Prior Art
In a previously proposed compressor arrangement disclosed in Japanese Patent Application First Provisional Publication No. 59-115490 the drive shaft of the compressor has been journalled in needle bearings or the like to reduce frictional losses. However, in the instance that such a compressor is used in the cooling circuit of an air-conditioner unit which uses a fluorocarbon refrigerant as the working fluid, during low thermal load operating conditions wherein the compressor is permitted to idle for relatively long periods, the needle bearing closest to the induction port of the device tends to be subjected to low temperature, high pressure conditions (e.g. 35 -36.degree. C. 8Atm) wherein the working fluid tends to mix with and dilute the oil (eg napthene class of lubricant) which lubricates the bearing in question. This phenomenon as shown in FIG. 5 has a detremental effect on the viscosity of the lubricant. Viz., as the amount of refrigerant (wt %) increases the kinematic viscosity of the oil (centistoke) rapidly drops.
Thus, in order to ensure that required characteristics of the lubricant are maintained in a manner which ensures the longevity of the bearing in question it is necessary to minimize the amount of dilution which occurs.
In order to overcome this problem it has been proposed in Japanese Patent Application First Provisonal Publication No. 60-98197 published on June 1, 1960 to provided a passage which leads from a chamber proximate the inboard end of the pump drive shaft and the needle bearing located distal from the induction port of the device, to a zone exposed to the high temperature high pressure pump discharge. A trigger valve is disposed in this pasage and arranged to close upon a predetermined discharge pressure being reached.
However, as this chamber communicates with the needle bearing proximate the inlet port of the pump via the vane reaction pressure chambers formed in the rotor, it has proven difficult to adequately maintain the temperature and pressure in and around the "induction side" bearing.